Nature Neuroscience (2010) doi:10.1038/nn.2562

しっかり読んでいませんが鍼により局所でadenosineが産生されadenosine A1受容体に働くことにより鎮痛が得られると結論しています。

これは中枢性の鎮痛でなく末梢での作用として説明できるようです。
こう考えられてきた鍼も一気に名誉挽回とは行くのか行かないのか

Despite thousands of years of anecdotal evidence claiming benefits in treating ailments from allergies to hiccups, acupuncture faces two big challenges to acceptance in mainstream medicine: most clinical trials have found no evidence of efficacy; and there is no scientifically accepted mechanism for how the treatment could work. Many researchers assume that any benefits are down to the placebo effect.